1. Field of the Invention
The present invention relates to an apparatus and method for testing a substrate, and more particularly to a substrate testing apparatus and method for testing a liquid crystal substrate employing an electron beam radiated from an electron gun.
2. Description of the Related Art
A substrate testing apparatus for testing a substrate is well known in which the substrate is tested by applying an electron beam from the electron gun to an object to be tested such as a liquid crystal substrate and detecting the X rays, secondary electrons or reflected electrons emitted from the substrate.
To apply electron beam onto the substrate, a range of the substrate for which the testing is performed is divided into a plurality of unit areas, in which the measurement is made for each unit area. In each unit area, the measurement is made by sequentially scanning electron beam over a predetermined number of measurement points. For the liquid crystal substrate, the unit area is set in a size of 45 mm×3 mm, for example.
The array of measurement points and the number of measurement points set in the unit area may differ depending on the object to be measured. For example, 900×20 or 320×60 measurement points are arranged for the unit area of 45 mm×3 mm.
FIGS. 5A and 5B are views for explaining the array of measurement points in the unit area.
FIG. 5A shows an example of the array of 900×20 measurement points. Substrate A is divided into unit areas of 45 mm×3 mm, each unit area having 900 points along a width of 45 mm and 20 points along a length of 3 mm, whereby measurement is made at a total of 18,000 measurement points in each unit area by applying electron beam to each measurement point.
FIG. 5B shows an example of the array of 320×60 measurement points. Substrate B is divided into unit areas of 45 mm×3 mm, like substrate A, each unit area having 320 points along a width of 45 mm and 60 points along a length of 3 mm, whereby measurement is made at a total of 19,200 measurement points in each unit area by applying electron beam to each measurement point.
In FIGS. 5A and 5B, an aspect ratio of unit area is not shown to be consistent with the ratio of 45 mm×3 mm for the simpler explanation.
To measure the unit areas of this liquid crystal substrate using the substrate testing apparatus, it is necessary to apply electron beam at each of the coordinate positions corresponding to the array of measurement points by scanning electron beam in one direction (e.g., x direction) while moving the liquid crystal substrate in the other direction (e.g., y direction) by driving the stage.
Since the array of measurement points in the unit area differs depending on the liquid crystal substrate species, it is required that the moving speed of the stage and the irradiating position of electron beam are varied for each liquid crystal substrate species to control the drive. Therefore, every time the liquid crystal substrate species which is an object to be tested is changed, it is necessary to change the scan parameters such as the stage speed and the irradiating position of electron beam.
In the related-art substrate testing apparatus, every time the liquid crystal substrate species which is an object to be tested is changed, the scan parameters of a control program for controlling the testing apparatus are changed, and the software for driving the apparatus is restarted after changing the scan parameters.
In the related-art substrate testing apparatus, because the stage speed and the irradiating position of electron beam are set as the scan parameters for the control program, to change the stage speed and the irradiating position of electron beam, it is required to change the scan parameters and restart the apparatus after changing the parameters, resulting in a problem in respect of the operability and the measurement time.